Syntax Style

Preferences in this section define how the implicitly typed local variables (also known as var keyword) should be used.

You can set different preferences of using 'var' or explicit type for different types:

• For built-in types — applies to C# built-in types.

• For simple types — applies to types without generic parameters.

• Elsewhere — applies to generic types and deconstruction declarations.

For each of these preferences you can opt for using 'var', explicit type, or 'var' when evident.

For more information, see Code Syntax Style: Implicit/Explicit Typing ('var' Keyword).

When configuring preferences of using 'var' keyword vs. explicit type, you can opt for Use 'var' when evident. This option seems self-explanatory but in some cases it might be unclear what is considered 'evident' and what is not.

Apart from that, there are some differences between what is considered evident (apparent) by ReSharper and by Visual Studio when both products suggest using 'var' keyword or explicit type.

Use this checkbox to apply Visual Studio logic for suggesting 'var' or explicit type when Use 'var' when evident is chosen in any options above.

To learn the differences between ReSharper and Visual Studio logic, see Use 'var' when evident: what is considered evident?.

This checkbox is enabled automatically when the csharp_style_var_when_type_is_apparent property in EditorConfig is set to true and has some severity level. For example: csharp_style_var_when_type_is_apparent = true:warning.

Preferences in this section define the style of namespace imports:

• Prefer fully qualified references — select this checkbox if you prefer use fully qualified names rather than namespace import directives for imported types.

• Add 'using' directive to the deepest scope — if this checkbox is selected, namespace import directives are added inside the namespace where the imported types are used; otherwise the import directives are added at the top of the file.

• Place 'System.*' and 'Windows.*' namespaces first when sorting 'using' directives — if this checkbox is selected, 'using' directives like using System.Linq; will be placed above other using directives when sorting. Otherwise, these directive will sorted alphabetically with others.

• Prefer fully qualified using name at nested scope — if this checkbox is selected, fully qualified names for imported types are preferred in nested types and namespaces.

• Allow using alias directive — selecting this checkbox allows using aliases in namespace import directives, as opposed to fully qualified namespace names.

• Allow the 'global::' prefix — if this checkbox is selected, the global:: prefix are not removed, as in global::System.String. For more information, see How to: Use the Global Namespace Alias.

A number of other options related to namespace imports can be configured on the Code Editing | C# | Namespace Imports page of ReSharper options.

Preferences in this section let you define which kinds of members should be declared with the expression body and which with the block body. For more information, see Configure preferences for expression-bodied functions.

By default, ReSharper applies heuristics to decide whether to convert block bodies of methods to expression bodies. Among other things, this means that ReSharper will not suggest expression bodies for void methods and for methods that contain a lambda expression.
You can simplify this logic by clearing the Apply style heuristics checkbox. In this case, the logic is simple: if you choose to use expression body for some kind of members, ReSharper will suggest expression body if the declaration of a member of this kind consists of a single statement.